llgo: Emit more debug metadata. For issue #49.
llgo: newStackVar split into newStackVar, newArgStackVar and *Ex

Also put in a new "var.go" file.
Merge pull request #78 from quarnster/debug

llgo: Emit more debug metadata. For issue #49.
pkg/runtime: fix jumped-over var decls
Merge branch 'master' of github.com:axw/llgo